2, 2-di(p-tolyl) propane preparation



11 Claims. or. 260-668) f The present inventionrelates to an improved process for the manufacture of 2,2-di'(p-tolyl) propane. More "ice ethane and nitropropane, and nitroaromatics as nitrobenzene, nitrotoluene, nitroxylene, nitronaphthalene and particularly, it is concerned with the condensation of 2-(p-tolyl)-2 chloropropane with toluene in the presence of acatalyst complex'comprising thechloride of hydrogen, the chloride of aluminum "and an organonitro com-.

pound; I v V v Considerable time, money and effort have been expendedin the development and commercialization of proc-.

esses leading to the preparation of 2',2 di(p-tolyl) propane. The latte'r'compound has gained prominence as .an article of "commerceand, particularly, as a valuable intermediate. For example, the corresponding oxidized product, 2,2-di-' (p-carboxyphenyl) propane, is useful as a compound inthe preparation of alkyd resins."

Until recently, most attempts at synthesizing di(p-tolyl). propane have been commercially unsuccessful. Recovery of the desired end product was unfortunately too small. Perhaps, the best of such processes is described in the recently issuedUnited States LettersPatent No. 2,719,871. Therein, the known reaction between aromatic hydrocarbons and 2-aryl-2.-chloropropane. in the presence of Friedel-Craft catalyst is markedly improved by adding hydrogen chloride to suppress the formation of by-product 1,3,3,6-tetramethyl-1-(p-tolyl) indane. Greatly improved yields were obtained. Nevertheless, theprocess still produced the desiredproduct and the indane derivative in the ratio of about 1.4:1, respectively.

It is an object of the present invention to provide a process for preparing 2,2-di(p-tolyl) propane by which this ratio is greatly improved to enable recovery of desired end product in yields hitherto unobtainable. It is a further object of the invention to provide a process for substantially reducing the formation of indanes and other contaminants. Other objects will become apparent to those skilled in the art from a reading of the specification as further detailed below.

According to the present invention, it has been discovered that the ratio can be increased to 10 to 1 or higher, by incorporating into the previously mentioned known reaction an organonitro compound at a temperature between minus C. and plus 30 C., and preferably between -l0 C. and +10 C. Unexpectedly, relatively small amounts of l,3,3,6-tetramethyll-(p-tolyl) indane are detected.

In general, a preferred procedure is to admix an organo-nitro compound and a Friedel-Craft catalyst in toluene. To the latter catalyst mixture is added 2- (p-tolyl)-2-chloropropane in sufiicient toluene containing hydrogen chloride. Alternatively, the organonitro compound may be added during reaction. However, the latter procedure is not preferred, due to the possibility of dimerization of the styrene resulting during the reaction and prior to its total addition.

The organonitro compound may be varied widely. For example, nitroalkanes and nitroaromatic hydrocarbon compounds are contemplated. Typically illustrative compounds are: nitroalkanes such as nitromethane, nitroequivalents thereof. In practice, the quantity of added organonitro compounds may also be varied. A good practice is the use of from about one (1) to about ten (10) molesof organonitro compound per mole of aluminum chloride. If 'a lesser mole quantity of nitro compound is used, somewhat reduced yields are noted. Larger amounts of thenitro compound may also be used. However, it has been found that such amounts do not materially add to the process in terms of yield, but detract economically from the process due to increased costs. A preferred range is one to five moles of the organonitro compound per mole of aluminum chloride.

The invention will be further described in the following examples which 'are merely illustrative and are not to be construed as being limitative. Unless otherwise stated, the parts given are by weight.

Example 1 A catalyst complex is prepared by charging to a suitable flask 174 parts of toluene (1.9 moles), 4 parts of anhydrous aluminum chloride (0.03 mole) and 10 parts of nitrobenzene (0.08 mole). The resultant clear, orange solution is next saturated with hydrogen chloride gas, while maintaining the contents therein at atemperature between 0 C. and 5 C. V

In a separate vessel equipped with stirrer, funnel, gas inlet and gas outlet, there is charged 87 parts of dry toluene. Sufficient anhydrous hydrogen chloride gas is then bubbled into the flask, While cooling the mixture to 0 C. to saturate the mixture. A solution of 40 parts of a-p-dimethyl styrene in 44 parts of toluene is next added slowly, while maintaining the solution saturated with hydrogen chloride and while agitating at such a rate that the resultant exothe'rm is controlled at a temperature below about 5 C. Resultant solution comprising 2- (p-tolyl)-2vchloropropane is'maintained at 0 C. or below under a stream of hydrogen chloride gas until the solution is added to' the'catalyst complex as prepared above: i

.The solution of 2-(p-tolyl)-2-chloropropane in toluene is now rapidly added to the catalyst solution with vigor ous stirring under a steady stream of hydrogen chloride gas. The mixture is stirred for an additional twenty minutes while maintaining the temperature at about 5 C. Thereafter, about 350 parts of cold water are added, with agitation, at such a rate so that the temperature is not permitted to rise above 25 C. An organic layer forms and is separated. It is washed twice with 10% sodium hydroxide solution followed by a water wash. The washed solution is then dried over anhydrous potassium carbonate.

The so-dried solution is next subjected to distillation under reduced pressure, whereby excess toluene and nitrobenzeneare removed. 2,2-di(p-tolyl) propane is distilled at 183 C. and 20 mm. Hg pressure. Resultant 2,2-di- (p-tolyl) propane solidifies upon cooling below 70 C. A yield of 56 parts corresponding to 82% is obtained. A second fraction is obtained by heating the remaining solution to a temperature of 198 C. and 20 mm. Hg pressure. Two (2) parts of compound (5%) corresponds to l,3,3,6-tetramethyl-1-p-tolyl indane.

From the above, it will be seen that the ratio of the di(p-tolyl) propane to the tetramethyl tolyl indane is 28 to 1.

Example 2 The procedure of Example 1 is repeated in every essential detail except that 5 parts of nitromethane are substituted for the nitrobenzene therein. The yield of 2,2-di- (p-tolyl) propane corresponds to 82% (56 parts) as in Example 1. Upon cooling, the latter compound solidifies and is recrystallized from methanol to give needles of 2,2-di(p-tolyl) propane of melting point 79 C. Both infira-red. and masssspectographic analysis indicate the correctness: of. thestructure of the product.-.-'- ;.,-As. in the previous example, a second, traction is obtained on vacuum distillation at 20 mm. Hg pressure by 111- crea'sing the temperature from; 183: C. to 198 .C.-,l--"1'-l1e distillate corresponds .to 1,3,3, tetramethyleldp-tolyl) indane. -A yield of 4 parts or ,1 -0,%.is obtained: a

,.It,is an advantage of the-presentinvention that a prooess is providedqfor increasing the, overall yieldaof de sired 2, 2-di(p tolyl) propane bysubstantially preventing the; formation; and. dimer-izationavofa-a-methy1p-methyl styrene from 2-;(p!toly1}r?a:chloropropane. a-Nonetheless, inthe absence of: anvorganonitro compound,--it-,-appears that-sufficient oep=dimethylvstyrene orits equivalent does form during. the overall condensation ,reactionv between the chloropropane and toluene-1reactantsrwl-lenca the yield of desired product is substantially reduced, notwithstanding the presence of added hydrogen chloride which functions 1 as -;a @dehydrohalogenation; suppressant; Even where react-ion: temperatures :resideiin the freezing range, dehydrohalogenation normallyzoccursas'evidenced byathe formation-of,substantial quantities of rdimerrv However, in :the presenceapf ran :organonitrovcompound t yields in excess; of '8 0%; 0i theoryrareriobtainedg thusnrenderingithe process of the present invention commercially feasible and attractive.

Weclaimz a T13 I 1.. In preparing-2;2-di(petolyl) .propane-by' reactlng a solution-:of -2- (p tolyl) -2-chloropropane .withtoluener'in the prese'nceof :anhydrous aluminum *chloride catalyst andasuflicient quantity of added hydrogen'chloride to saturate said solution,-itheimprovement'therein which comprises: carrying :out' the reaction in the-f'presence of a catalyst. complex comprising aluminumxchlorida hy drogenichloride, toluene and-raniorganonitro compound selected from the group consisting of a nitroalkane and a nitroa'romatic:hydrocarbon. 'i a 2. A process according to claim'l in which the organt nitro compound is added in an amount sutficient tozisupply from about 1 to 10 moles per mole of aluminum chloride,

3 A processaccordingto claim 1 in which the reaction temperature is in the range of from about minus 30 C. to plus 30 C.

4. A process according to claim 1 in which a catalyst complex comprising aluminum chloride, hydrogen chloride, toluene and an organonitro compound is formed prior to use.

5. Ai processiaccording toclaim 4 -in which the organonitro compound is nitromethane. r V

process accord" g to claim 4 in which the organonitrocornpoundfis"nitroethaner 7. A process according "to claim 4 in which the organonitro com'p'ouud is fiitiopr'opanei A -r-;==

8 A process vaccording to claim A in which the organonitro compound'isnitrobenienf 9. A process according to claim 4 in which the organonitro compound is nitrotoluene. 1 -tlthaAfi:improvethprocesston preparing 2;2-di(p-tolyl) propane =whichncomprises'ii reacting 2-:(p-tblyl)*-2-chloropropatieswithtoluene irflthe presence'of anhydrous-aluminunrzch'lorid'escatalyshand' both"- aisuflicient quantity of added hydrogen chloridezand nitroberizene at a temperature'ofialiouttili G. to 5% C.; said rnitrobenzene being present in a quantity equal to 2.7 moles of the latter permole of .athe alhminu'mi'chlorideacatalyst' on aaweig ht'fbasis; dilutingiitheoreactiom.mixtureiwith water, and recovering resultant 2'g2 dip-tolyl)"propaneills" W 'LiaAzeicomplexscatalystsicomposi ueneasaturatdwith hydrogtchldride gas and containingdi'ssolvedatherein 'l to l-0 inoles -of an organonitro com= poundi per mole of .alixmimimchloride; saidforganonitro compound being selected-Hiram th group consisting of a nitroalkane and a nitroaromatic hydrocarbon.

Reference Cited the-ziilei'of vthis patent NITED AT S PA N S 72,076,201 La' i TAir.6, 1937 2,302,721 'Schinei'ling' Nov. 24, 1942 2,385,303 Schm'erlih'g Sept. 13, 1945 2,406,639 Schmefling- "Aug. 27, 1946 2,719,871 Hiatt' Oct.4, 1955 2,756,265. Hbuydaysr July 24, 1956 2,794,822 'Schweitzer June 4, 1957 tlon comprising: tol- 

1. IN PREPARING 2,2-DI(P-TOLY) PROPANE BY REACTING A SOLUTION OF 2-(P-TOLYL)-2-CHLOROPROPANE WITH TOLUENE IN THE PRESENCE OF ANHYDROUS ALUMINUM CHLORIDE CATALYST AND A SUFFICENT QUANTITY OF ADDED HYDROGEN CHLORIDE TO SATURATE SAID SOLUTION, THE IMPROVEMENT THEREIN WHICH COMPRISES: CARRYING OUT THE REACTION IN THE PRESENCE OF A CATALYST COMPLEX COMPRISING ALUMINUM CHLORIDE, HYGROGEN CHLORIDE, TOLUENE AND AN ORGANONITRO COMPOUND SELECTED THE GROUP CONSISTING OF A NITROALKANE AND A NITROAROMATIC HYDROCARBON. 